This is a bad idea for the reasons that other commenters have already stated. If WayBackMachine falls, all links would fall. Actually the "Web" would stop being one, if all links are all within the same service.

For docs and other texts, I just link to the original site and add an (Archive) suffix, e.g. the "Sources" section in https://doc-kurento.readthedocs.io/en/latest/knowledge/nat.h...

That is a simple and effective solution, yes it is a bit more cumbersome, but it does not bother me.